enter image description hereenter image description hereenter image description hereWhat is this?

What is this tool used for? it seems to be a stainless tool steel and has a round shaft with a triangle tip.

  • Some type of punch. Another picture of the tip/end might help. Right now it looks kind of flat.
    – crip659
    Commented Dec 13, 2022 at 21:13
  • the tip is flat, possibly looks like something has snapped off it.
    – sammckay
    Commented Dec 13, 2022 at 21:29
  • New pictures help. Looks like a grounded edge(abused), so maybe a chisel/punch.
    – crip659
    Commented Dec 13, 2022 at 21:37
  • 1
    An end mill someone abused as a punch. Google brenco and you get "Lathes + Machine Tool Archive"
    – Mazura
    Commented Dec 14, 2022 at 0:49
  • 1
    someone has been using it as a punch (because the other end is mushrooming) but I don't think that was the original purpose.
    – Jasen
    Commented Dec 14, 2022 at 1:32

1 Answer 1


It's a VERY limited use security bit, for screws generally used to secure wall panels in private spaces prone to vandalism. (I've mostly seen them in boy's bathrooms in schools). It's often called a tri-star bit.

  • it seems kind of flat faced, tri star is not particularly obscure.
    – Jasen
    Commented Dec 14, 2022 at 1:46
  • 2
    This was my initial thought, but... it's got a round shank, not hex, so it won't fit an impact driver (where 99% of bits are meant to go these days). There aren't any scratch marks on the shank from having been tightened down into a normal 3-jaw chuck (if it's much older). It's quite rather long to be a driver bit. OP believes it to be stainless steel which is rather uncommon for use as tool steel - it's too brittle.
    – FreeMan
    Commented Dec 14, 2022 at 17:24

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